Salt Lake Sechi in China, often called the “Chinese Dead Sea”, attracted crowds of tourists. Algal blooms and rapidly breeding insects colored its waters in bright shades of purple, green and yellow.
The reason for the rare phenomenon is algae species Dunaliella salina, which, according to NASA, look green in the marine environment, but can turn red. In conditions of high salinity and light intensity, they begin to produce protective carotenoids in cells. These plant pigments are responsible for the bright color of the lake.
A study conducted by experts from the University of Concepción in Chile showed that D. salina algae are currently the most resistant to high concentrations of salts by eukaryotes. They can be found in salt lakes around the world – in Chile, Mexico, Australia and Israel.
Some strains of algae can accumulate more than 10% of their dry weight of β-carotene if they are exposed to stressful conditions such as intense irradiation, high salinity, lack of nutrients or extreme temperature, making them the richest natural source of this pigment. D. salina is used in cosmetics, in multivitamins and as a food color.
Lake Sechi (Xiechi) is located near the city of Yuncheng. It was formed about 500 million years ago and for 4000 years served as a source of salt for the local community. It is the third largest sulphate lake in the world, the area of which is 120 square kilometers.
Like in the Israeli Dead Sea, it has many minerals useful to the skin. But if the black mud of the Dead Sea contains mainly chlorides, then the basis of the Chinese lake is sulphates, so that it can support a rich variety of flora and fauna.
Unfortunately, the flowering of algae sometimes causes an excess of nutrients in the water, which threatens the appearance of a dead, or hypoxic zone. As the algae spread, their number can reach millions of cells per milliliter, suppressing other life forms that die and then decompose by bacteria. This organic decay depletes the oxygen available in the water. Many fish and insects can not survive in such conditions.